There is known a flush toilet in which a toilet seat is placed on a rim of a toilet body with the toilet seat free to open and close on a pivot axis that is on a side of a rear end thereof, and in which a toilet seat cover is placed so as to cover the toilet seat with the toilet seat cover free to open and close on the same pivot axis as that of the toilet seat or another pivot axis.
In such conventional flush toilets, there are provided various prevention methods for preventing human liquid waste in sitting position or flush water causing dirt from flowing out from a gap between a front upper face of a rim of a toilet body and a front lower face of a toilet seat. For example, JP Pub No. 2007-191909 (hereinafter called “Document 1”) discloses that a projection rib for preventing dirty water from flowing out is formed on the front upper face of the rim of the toilet body along an outer peripheral edge thereof and that a groove configured so that the projection rib is fit into the groove when the toilet seat is in closing state is formed in a side of the lower face of the toilet seat. The groove is provided therein with a soft packing member adapted to be in contact with the projection rib.
Though the prior art described in Document 1 can prevent dirty water (liquid waste and flush water) from flowing out, the groove becomes unclean because the dirty water is accumulated into the groove in the side of the lower face of the toilet seat. This requires frequent cleaning of the groove. Moreover, the cleaning of the groove is not easy.